The invention relates to a circuit arrangement for generating the vertical synchronizing information in a magnetic video-tape apparatus in which the magnetic tape is at least partly wrapped around a rotating head-support and the head support carries one or more magnetic heads which are uniformly spaced over the circumference of the head support, which magnetic heads consecutively write or scan adjacent tracks on the magnetic tape which tracks are inclined relative to the longitudinal axis of the magnetic tape and each contain the information of one field and at a predetermined small distance from the edge of the magnetic tape contain the vertical synchronizing information, a track-change signal being generated, which signal is synchronized with the head-support rotation and indicates a track change, and which apparatus further comprises a line-pulse generator for generating a line-pulse signal, which generator is synchronized by the horizontal synchronizing pulses in the video information.
Such magnetic video tape equipment is generally known and is described in, for example, "Heimvideotechnik" (Special Issue of Funkschau), Franzis-Verlag 1979 on pages 5 to 10. Since the tracks not only contain the picture information but also the complete synchronizing information, the signal which is read from the tracks during playback and which is demodulated in the video processing circuit constitutes the complete CVBS signal which is applied to a television set for reproducing the picture information.
In practice it may happen that at least locally the edge of the magnetic tape is damaged or stretched, resulting in curled edges or folded portions parallel to the edge of the magnetic tape, which may be caused by faults in the manufacture of the magnetic tape or by the use of the magnetic tape in an apparatus which is not in good condition. As a result of this, it is not possible to scan the vertical synchronizing information from these damaged locations of the tape, so that the picture reproduced on the television set is not synchronized and "rolls".